Cellular communications networks utilize handover procedures to accommodate movement of mobile terminals between cells of the cellular communications network while in a connected state. As part of the handover procedure, a network node (e.g., a base station) decides, at an appropriate time, whether to perform a handover of a mobile terminal from one base station to another. In general, handover decisions are made based on a margin hysteresis for signal strength and a time hysteresis. The rationale behind this signal and time hysteresis is to avoid oscillations between neighbor cells; these oscillations are referred to as “ping-pongs.” In 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE) cellular communications networks, handover decisions are made based on a handover (HO) hysteresis and a Time to Trigger (TTT) parameter. More specifically, in 3GPP LTE cellular communications networks, a serving base station decides whether to perform a handover for a mobile terminal (i.e., a User Equipment (UE)) from the serving base station to a target base station based on the equation:RSRPTARGET>RSRPSERVING+HOHYSTERESIS+CellOffset,where RSRPTARGET is a Reference Signal Received Power (RSRP) of the target base station measured at the mobile terminal, RSRPSERVING is a RSRP of the serving base station measured at the mobile terminal, HOHYSTERESIS is the handover hysteresis for signal strength, and CellOffset is a cell specific offset. It should be noted that the equation above is a simplified version of the equation which is found within the 3GPP specifications; however, the main content of the equation in the 3GPP specifications is included in the equation above. The serving base station decides that a handover is to be performed to the target base station when the equation above has been satisfied for an amount of time defined by the TTT parameter.
Values for the handover parameters HOHYSTERESIS, CellOffset, and TTT are set for an operator of the cellular communications network and are typically the same for all mobile terminals within a given cell. However, the 3GPP LTE standard allows the setting of these handover parameter values on a per mobile terminal basis. For instance, the handover parameter values can be selected upon consideration of a speed of the mobile terminal, a cell size of the serving base station, a direction of movement of the mobile terminal, a cell load of the base station, and/or characteristics of the serving base station. It is also possible to set the handover parameters on the basis of the type of service running on the mobile terminal. Thus, the handover parameters may be set to different values for time critical services (e.g., video or speech) versus best effort services (e.g., web or File Transfer Protocol (FTP)). In this manner, handover decisions can be optimized. However, further optimization of the handover decision is desired in order to further improve the performance of the cellular communications network.